A communication system provides a mechanism by which to communicate communication data between communication stations of a set of communication stations. At least one of the communication stations of the set forms a sending station. And, at least another of the communication stations of the set of communication stations forms a receiving station. Communication data originated at or, otherwise provided to, a sending station is communicated to a receiving station by way of a communication channel. The receiving station operates to detect the communication data communicated upon the communication channel and to recover the informational content thereof.
Different types of communication systems have been developed and deployed to effectuate different types of communication services. As advancements in communication, and other, technologies permit, new types of communication systems are developed and deployed. And, existing communication systems are adapted, also to make use of the technological advancements.
A radio communication system is an exemplary type of communication system. Various radio communication systems have been made possible as a result of technological advancements. And, existing radio communication systems have also benefited from technological advancements.
A radio communication system differs with a conventional wireline communication system in that the communication channel that connects communication stations operable therein is defined, at least in part, by a radio channel formed on a radio link extending between the communication stations. The need to use a wireline to interconnect the communication stations is obviated.
Various advantages are provided when the need for a wireline connection is obviated. Communications between locations at which wireline connections would be inconvenient or impractical are facilitated as radio channels are used upon which to communicate the communication data. And, a radio communication system is implementable as a mobile communication system in which one or more of the communication stations of the communication system are permitted mobility. Additionally, the costs associated with initial deployment of a radio communication system are generally less than the costs associated with initial deployment of a wireline counterpart. Accordingly, a radio communication system is generally more economically implemented and a corresponding wireline counterpart.
Many modern radio, as well as other, communication systems make use of digital communication techniques. When digital communication techniques are utilized in the communication system, the communication data that is to be communicated is by a sending station is digitized, and the communication data, once digitized, is communicated. In a packet communication system, the data is formatted into packets or frames of data. When formatted into the packets or frames, for instance, the packets or frames are communicated during discrete intervals.
If the communication channel upon which the communication data is communicated is free of distortion, values of the communication data, when received at the receiving station, identically correspond in values with corresponding values of the communication data when sent by the sending station. Communication channels, however, are not ideal. The values of the communication data differ, due to their communication upon a non-ideal communication channel, in value with the values when sent by the sending station. Additional distortion is sometimes further caused at the receiving station as the communication data is operated upon, prior to recovering the informational content thereof.
Channel conditions on a radio communication channel are sometimes particularly problematical. Multi-path communication conditions on a radio channel, for instance, cause communication data to fade during its communication thereon to a receiving station. Multi-path transmission conditions are sometimes referred to as being fading conditions. Fading of the communication data alters the values of the communication data, or portions thereof, such that, when detected at the receiving station, the values of the communication data differ with corresponding data when sent by the sending station.
Various manners are conventionally used by which to attempt to compensate for the distortion introduced upon the communication data. For instance, by increasing the diversity of the data, through the use of a diversity technique, the likelihood that the informational content of the communication data can be recovered at the receiving station is generally increased.
And, in a communication system that utilizes multiple transmit antennas, such as in a multiple-input, multiple-output communication system, spatial multiplexing is sometimes used. The use of spatial multiplexing compensate for the distortion.
While both techniques, i.e., diversity techniques and spatial multiplexing techniques, each provide separate manners by which to increase the likelihood that the informational content of the communication data can be recovered, such techniques are generally not used together. The complexity required of decoder apparatus at the receiving station would be so computationally intensive as to be prohibitive to implement. Conventional manners by which to form the communication data according to diversity and spatial multiplexing techniques would require large constellation sizes and trellises having numerous states. The computational complexity of a maximum likelihood decoder would not be practical to implement, especially when the decoder would be required to operate upon communication data communicated at high data rates. Alternately, iterative decoding techniques could be attempted. However, conventionally, mutual interference would cause iterative solutions to converge to incorrect local minima.
While the use of both diversity and spatial multiplexing techniques, used together, would improve the likelihood that the informational content of communication data could be recovered, the impracticality of its implementation in conventional systems has prevented their use together in a communication system. If a manner could be provided by which to utilize both diversity and spatial multiplexing techniques in a communication system, improved communication performance of the communication system would be possible.
It is in light of this background information related to the communication of communication data in a communication system susceptible to distortion that the significant improvements of the present invention have evolved.